Method for making net-like structures of curved construction

ABSTRACT

Method for making net-like structures of curved construction in which composite extrusion nozzles are each turned through an angle of 180* alternately with relative movement between nozzle sections along arcuate paths extending about a common center.

United States Qatent Fairbanks 51 Aug. 22, 1972 [54] METHOD FOR MAKINGNET-LIKE 3,012,275 12/1961 Nalle ..264/DlG. 81 STRUCTURES OF CURVE!)3,331,903 7/ 1967 Mine ..264/DlG. 81 CONSTRUCTION 3,360,410 12/1967Romanin ..264/DlG. 81 [72] Inventor: Theodore Fairbanks RD #1, 3,518,7207/1970 Fairbanks ..18/8 Liverpool Pa 17045 3,562,046 2/1971 Guy..156/167 3,579,729 5/1971 Fairbanks ..18/12 N dl Jan- 5, 19 1 3,591,8927/1971 Fairbanks ..264/167 21 Appl No; 104 08 3,591,894 7/1971 Fairbanks..264/167 Related US Application Data FOREIGN PATENTS OR APPLICATIONS 3continuationdmpart f Ser. 4 009 Aug 380,369 9/1964 Switzerland..264/DIG. 81

6, 1969, Pat. No. 3,601,850. V Primary ExaminerJay H. W00 [52] vs. C]...264/103, 87/1253, 156/167, Attorney-Thomas oMalley, George Muellerl61/D1G. 6, 264/167, 264/DIG. 81 and Eugene Horsky [51] Int. Cl ..D04g1/00, D02g 1/20 [58] Field of Search ..264/DIG. 81, 167, 103; ABSTRACT18/12 8 13 N; 161/1316 Method for making net-like structures of curvedconstruction in which composite extrusion nozzles are each turnedthrough an angle of 180 alternately with [56] References cued relativemovement between nozzle sections along ar- UNITED STATES PATENTS cuatepaths extending about a common center.

3,630,117 12/1971 Guy .L ..264/103 3Claims, 4Drawing Figures METHOD FORMAKKNG NET-LIKE STRUCTURES OF CURVED CONSTRUCTION This application is acontinuation-in-part of my application Ser. No. 848,009, filed Aug. 6,1969 now U.S.

. each pair of filaments are revolved, at the amount of their extrusionand before being solidified, about an axis extending between thefilaments of each pair of filaments so as to twist the filaments of eachpair together and to thus integrally connect the same. One of thefilaments of each pair of filaments is then moved in a second directiona distance equal to the spacing between pairs of filaments whilecontinuing the extrusion of the filaments, afterwhich the pairs offilaments are again revolved as heretofore described. By continuouslyrepeating the above steps and setting the extruded filaments of plasticmaterial, a net is provided.

The above-noted United States patent is concerned primarily with amethod and apparatus for making a flat net, but does suggest that theteachings set forth therein are adapted also for making a tubular net.Of importance, however, is that regardless of the shape of the netproduced the filaments forming such net are revolved through one or morecomplete revolutions as they are extruded and while they are still in aplastic condition so as to twist and integrally connect or bond the sameto each other at their locations of twisting.

A primary object of this invention is to provide a generally new orimproved and more satisfactory method for making net-like structures ofcurved or tubular construction by extrusion.

Another object of this invention is a new or improved method for making,by extrusion, continuous woven or braided net-like structures of curvedor tubular construction.

Still another object is the provision of a method for making, byextrusion, woven or braided net-like structures of curved constructionhaving a variety of interlaced strand or filament patterns.

These and other objects are accomplished in accordance with the presentinvention by a method in which a plurality of pairs of continuousstreams of flowable strand-forming material are extruded in spacedrelationship, with the streams in each such pair being located alongopposite sides of a common arc or circle. The streams of at least someand preferably all pairs of streams are turned through an angle of only1 80 or further multiple of 1 80 about an axis extending between therespective streams of each such pair of streams. Once turned, thestreams of each such pair of streams are moved relatively in directionsconcentric with the arc or circle along which they are extruded toarrange at least certain of the streams of each pair of streams intodifferent pairs. The streams of strandforming material are setconcomitantly with their extrusion, either prior to or after contacttherebetween. By continuously repeating the above sequence of movements,with the continuous extrusion of the streams of strand-forming material,a net-like structure of curved or tubular construction is produced.

The streams of each pair of streams need not be spaced equal distancesfrom the common are or circle along which they are extruded, nor is itessential that the spacing between streams of all such pairs of streamsbe the same. The plurality of pairs of streams may be disposed generallyalong an arc of 360 or less, preferably with the axes about which therespective pairs of streams are turned being spaced equal angulardistances from each other.

Relative movement of the streams of at least some and preferably allpairs of streams is effected, desirably but not necessarily, by movingthe streams of each such pair of streams oppositely of each other indirections concentric with the arc or circle along which they areextruded. During such movement the streams of each pair of streams maybe moved a distance equal to onehalf of the angular spacing betweenadjacent pairs of streams or a further multiple thereof. It will beapparent that this relative movement of the streams of each such pair ofstreams may be varied either periodically or randomly throughout themethod, providing it is a multiple of one-half of the given distancebetween the adjacent pairs of streams, to provide net-like structureswith different strand patterns along their lengths.

When the plurality of pairs of streams are disposed generally along anarc of less than 360, it is essential that the direction in which thepairs of streams are turned be reversed after each relative movement ofthe streams of such pairs, and that the direction of movement of therespective streams of each pair of streams during the relative movementthereof be reversed after each turning 'of the pairs of streams. Thissame procedure may be employed but is not essential when the pluralityof pairs of streams are extruded at spaced intervals along an arc of360. In this latter array of streams, the pairs of streams may be turned180 in the same direction after each relative movement between streamsof such pairs, provided there is no reversal in the direction in whichcorresponding streams of the different pairs of streams are moved duringtheir relative movement.

In the resulting net-like structure, the strands will be interlaced witheach other in a woven or braided construction, or may be twistedtogether, depending upon the angle through which the streams formingsuch strands were turned during and/or following their extrusion.Setting of the extruded streams into strands may be effected prior toany contact between the extruded streams whereby the strands in theresulting netlike structure would be unbonded at their locations ofcrossing. Alternatively, the extruded streams may be set into strandsafter such streams have made contact with eachother so that the strandsin the resulting netlike structure would be bonded to each other attheir locations of crossing.

The apparatus employed in the method of the present invention includes aplurality of composite nozzles each including a pair of like extrusionsections and a spacer section positioned therebetween. The nozzleextrusion and spacer sections are formed with mating arcuate walls withthe arcuate walls of all extrusion sections being-of like radius. Theseextrusion sections are supported in spaced apart relationship with anarcuate wall of one such section of each of the plurality of nozzlesextending along a common are or circle having a radius equal to that ofsuch arcuate walls.

Means are provided for intermittently turning nozzles through an angleof only 180 or further multiple of 180 about an axis located midwaybetween the arcuate walls of the extrusion sections of such nozzles, andalso for relatively moving the extrusion sections of each of the nozzlesto rearrange the same into alignment with like extrusion sections ofother of such nozzles. The means for effecting relative movement of thenozzle sections is operative alternately with the nozzle turning meansand serves to move corresponding extrusion sections of the respectivenozzles simultaneously and in the same direction along paths concentricwith the common are or circle.

At least one orifice extends through each of the nozzle extrusionsections and means are provided for delivering flowable strand-formingmaterial to such orifices. Means are also provided for setting thestreams of strand-forming material which are extruded from the orificesin the nozzle sections.

The arcuate walls of the nozzle extrusion sections may be of eitherconvex or concave configuration, with the walls of the spacer sectionsbeing shaped to mate therewith. The apparatus may include at least onepair of nozzles in which the arcuate walls of the extrusion sections areof convex configuration and/or at least one pair of nozzles in which theextrusion sections have arcuate walls of concave configuration. Whilethe arcuate walls of all of the nozzle extrusion sections must be oflike radius, such radius may be varied; the smaller the radius, the morepronounced is the curvature of the resulting net-like structure.

In the apparatus employed in the method of the present invention formaking tubular net-like structures, the nozzle supporting means includesa pair of concentric annular members, one of which is disposed with itsouter peripheral surface slidably engaging with the inner peripheralsurface of the other of such annular members. Cooperating recesses areformed along the contacting peripheral surfaces of the annular membersand together define openings in which the composite nozzles arerotatably carried. in such apparatus, at least one of the annularmembers is driven, after each turning of the nozzles, in a directionwhich is the same or opposite to its prior movement. As heretoforementioned, reversal in the direction of relative movement of the nozzleextrusion sections requires that the direction of nozzle turning also bereversed.

Tubular net-like structures formed in accordance with the presentinvention are particularly suited for use in the packaging of produce,such as potatoes, onions, etc. Net-like structures having a curvature ofless than 360, say 180 or 270, may be combined to provide corrugatedmembers which are suitable for use, for example, as shock absorbinginsulation means.

The teachings of the present invention are applicable for use with avariety of materials, which are referred to by the terms plastic" orstrand-forming materials, including polyolefins, such as polyethylene,polypropylene, polybutylene, polystyrene, polystyreneacrylonitrileblends, acrylonitrile butadiene-styrene blends, acrylonitrile-butadienecopolymers, polybutene, polyisobutylene, polyisoprene, andisobutyleneisoprene copolymers; halogenated olefins, such aspolyfluoroethylene, polychlorofluoroethylene, polychlorofluoropropylene,polyvinyl chloride, polyvinylidene chloride, polyvinyl chlorideacetatecopolymer, polyvinyl chloride-polypropylene copolymer, polychloroprene,fluoroinated ethylenepropylene copolymers, vinylidenefluoridechlorotrifluoroethylene copolymers, and vinylidenefluoride-hexafluoropropylene copolymers; polyesters, such aspolyethylene terephthalate and copolymers thereof and polycarbonate;polyamides, such as polyhexamethyl adipamide, polyeaprolactam,polyhexamethylene sebacamide, poly-aminoundecanoic acid; polyvinylacetates; chlorinated polyethers, such as, ethylacrylate-chloroethylenevinyl ether copolymer; acrylic resins, such as polyacrylonitrile,polyacrylates and methacrylates; natural rubbers; compounded silicones;polyurethanes; polyethers; such as polyformaldehyde,formaldehyde-ethylene oxide copolymers, and polytrioxane; polysulfurresins, such'as polysulfones and polysulfides; water-soluble, alkalisoluble, and organic solvent-soluble cellulose esters and ethers, suchas cellulose nitrate, cellulose acetate, cellulose butyrate, cellulosepropionate, ethyl cellulose, viscose or cellulose xanthate,cuproammonium cellulose, and carboxymethyl cellulose; glasses; metals,etc. Such materials may include various additives such as stabilizers,dyes, foaming agents, etc., if so desired. It will be apparent that themanner by which the extruded streams are set will depend upon theparticular plastic or strand-forming material which is being employed.

For a greater understanding of this invention, reference is made to thefollowing detailed description and drawing in which FIG. 1 is adiagrammatic view showing a portion of an apparatus employing teachingsas suggested by U.S. Pat No. 3,331,903;

FIG. 2 is a view similar to FIG. 1 of a modified apparatus;

FIG. 3 is a view similar to FIG. 1 illustrating nozzles employed in theapparatus used in the method of the present invention;

MG. 4 is a partial plan view of the apparatus used in the method of thepresent invention; and

HG. 5 is a section taken vertically through the apparatus shown in FIG.3.

As heretofore mentioned, U.S. Pat. No. 3,331,903 discloses a method andapparatus for making nets by extruding filaments of plastic material andperiodically twisting such extruded filaments with each other one ormore complete revolutions while they are still in a tacky condition tothus provide integral filament junctions.

More specifically, the apparatus described in the above United Statespatent includes two sets of nozzle members, each having a peripherydefined by a semicircular wall and a flat wall, and each being formedwith a bore for extruding a filament therethrough. The nozzle members ineach set are spaced from each other a given distance and the nozzlemembers in the two sets are respectively arranged closely to each otherto form pairs of adjacent nozzle members. Means are provided forrevolving each pair of nozzle members about an axis located between thebores thereof and for shifting the nozzle members of one set through thegiven distance of spacing so that each nozzle member of the one set isagain closely arranged to a respective nozzle member of the other set toform a pair of adjacent nozzle members.

In the apparatus specifically described and illustrated in U.S. Pat. No.3,331,903 the two sets of nozzle members are arranged in straight rows.The patentee does suggest, however, that it is also possible to arrangesuch sets of nozzle members along two concentric circles. This latterarrangement is illustrated in FIG. 1 of the accompanying drawing whereinnozzle members 11 of one set and nozzle members 13 of a second set arecarried by annular supports 15 and 17, respectively. The periphery ofeach nozzle member of both such sets is defined by a semi-circular wall19 and a flat wall 21, and each such members is provided with anextrusion bore 23.

In accordance with the method described in the above-noted U.S. patent,plastic material would be delivered to each of the nozzle members 11 and13 of both sets of such nozzle members and would be extruded from thebores 23 as filaments. The nozzle members of the two sets, being alignedin pairs, would then be revolved through one or more completerevolutions by suitable means, not shown.

Continuing with the method as disclosed in the above-cited patent, oneset of nozzle members would now be shifted so as to rearrange the nozzlemembers of such one set with different nozzle members of the other ofsuch sets. It will be noted, however, that portions of the nozzlemembers 13 of one such series project beyond the inside peripheral wall25 of the annular support 15 and thus neither of the annular supports115 or 17 can be moved about its axis. Shifting of the nozzle members ofone set of nozzle members relative to the other set thereof, as isrequired in the method disclosed in the cited patent, cannot be achievedand the apparatus shown in FIG. 1 of the accompanying drawing isconsidered inoperative.

While not disclosed nor suggested in the above-noted U.S. patent, theapparatus shown in FIG. I of the accompanying drawing may be modified torender the same capable of making net structures. As shown in FIG. 2 ofthe drawing, two sets of nozzle members 27 and 29 are carried by annularsupports 31 and 33, with each nozzle member having an extrusion bore 35.These two sets of nozzle members differ from those shown in FIG. 1 inthat the nozzle members 27 of one such set are each formed with anarcuate wall 37 which mates with an arcuate wall 39 formed on each ofthe nozzle members 39 of the other of such sets. The menate walls 37 and39 of the nozzle members are of like radius, which is equal to that ofthe peripheral walls 41 and 43 of the annular supports 31 and 33,respectively.

In using the apparatus shown in FIG. 2 of the accompanying drawing, eachpair of aligned nozzle members must be revolved one or more completerevolutions alternately with the shifting of one set of nozzle membersrelative to the other of such sets to rearrange the same into differentpairs. When revolved, it is essential that the pairs of nozzle membersof this apparatus be turned through one or more complete 360revolutions.

Failure to observe this limitation will render the apparatus of FIG. 2inoperative. For example, moving the pairs of nozzle members through anangle of only 180 or further odd number multiple of 180 would disposethe nozzle members as shown at the lowermost portion of FIG. 2. In thisposition of the nozzle members, neither of the annular supports 31 or 33is capable of turning about its axis and thus shifting of one set ofnozzle members relative to the other of such sets could not be achieved.

From the above description it is believed clear that the apparatus shownin FIG. 1, which corresponds with that suggested in U.S. Pat. No.3,331,903, is inoperative while the apparatus shown in FIG. 2 is adaptedto provide only net structures having integral junctions at whichfilaments are twisted together through one or more turns.

The apparatus employed in the method of the present invention is alsocapable of providing nets as formed by the apparatus shown in FIG. 2but, more important, is adapted for use in the manufacture of netlikestructures of curved or tubular construction in which strands orfilaments are interlaced with each other in a woven or braidedrelationship.

Referring to FIGS. 3-5 of the drawing, the illustrated apparatusincludes a pair of concentric cylinders 45 and 47 which are held infixed positions by suitable supporting structures, not shown. At theirlowermost ends, the cylinders 45 and 47 each include an integral flange49 and 51, respectively, on which are slidably carried a pair ofconcentric, annular nozzle support members 53 and 55. Split rings 57 and59 are seated within grooves 61 and 63 formed in opposing walls 65 and67 of the cylinders 45 and 47, respectively, and serve to retain theannular members 53 and 55 against the cylinder flanges.

At least one of the annular members 53 and 55 is adapted to be rotatedor oscillated about its axis and in the preferred construction both suchmembers 53 and 55 are capable of rotation. As shown in FIG. 5, gearteeth 69 are machined into the bottom wall 71 of the annular member 53at a location adjacent to its outer periphery, while like gear teeth 73are fonned in the bottom wall 75 of the annular member 55 but adjacentto its inner periphery. One or more openings 77 are provided in each ofthe cylinder flanges 49 and 51 for accommodating gears 79 and 81 whichmesh with the teeth 69 and 73, respectively, formed in the annularmembers 53 and 55. The gears 79 and 81 are fixed, respectively, toshafts 83 and 85 which pass through openings 87 in the cylinders 45 and47 and are intermittently driven by suitable means, not shown.

Opening along contacting peripheral surfaces 89 and 91 of the annularmembers 53 and 55 are recesses 93 and 95, respectively, which are oflike radius and, when aligned with each other, together define circularopenings within each of which is disposed a composite, circular nozzle,As more fully described hereafter, the composite nozzles are retainedwithin the aligned recesses in the annular members 53 and 55 by flangeportions formed along the uppermost ends thereof.

In FIG. 3 are illustrated various forms of composite nozzles 97, 99 and1011 which are suitable for use in the apparatus used in the method ofthe present invention. The nozzles 97, 99 and 101 all include a pair oflike extrusion sections 103, each having arcuate walls 105 and 107, andthe spacer section 109 having like arcuate walls 111 which mate with thewalls 107 of the extrusion sections. The arcuate walls 105 of the nozzleextrusion sections 103 are of a radius substantially equal to that ofthe recesses 93 and 95 in the annular members 53 and 55, while the walls107 thereof are of a radius substantially equal to that of theperipheral surfaces 89 and 91 of the annular members 53 and 55. Commonalso to each of the different forms of nozzles 97, 99 and 101 is atleast one orifice 113 extending through each of the extrusion sections103.

The composite nozzles 97 99 and 101 are of like circular cross-sectionand differ only in the size and/or shape of the sections thereof. Moreparticularly, the spacer section 103 of the nozzles 97 and 99 are oflike configuration and differ only in size. Thus the spacer section 109of the nozzle 97 is larger than the spacer section 109 of the nozzle 99and includes also arcuate walls 115 which form part of the nozzleperiphery. On the other hand, the nozzle 101 differs from the nozzles 97and 99 in that the arcuate walls 107 of extrusion sections 103 are ofconvex configuration while the mating walls 111 of its spacer section109 are concave in shape. The spacer sections 109 of the nozzle 101 alsoincludes arcuate walls 117 which form part of the nozzle periphery.

The plurality of nozzles employed in the described apparatus may bealike. Alternatively, the nozzles may differ in size and/or shape. Forexample, at least one pair of each of the different nozzles may bepresent in the same apparatus. For simplicity and ease of description,all composite nozzles employed in the apparatus shown in FIGS. 4 and areof like size and shape and correspond to nozzles 97 shown in FIG. 3.

The nozzles 97 each include flange portions 119 and 121 projecting fromthe extrusion and spacer sections, respectively, which are adapted torest upon the top surfaces of the annular members 53 and 55. Each of thenozzles 97 is adapted to be periodically turned about its axis throughan angle of only 180, or further multiple thereof, and for this purposeare provided with gear teeth 123. Ring gears 125 and 127 mesh with theteeth 123 on the nozzles 97 and, when driven, serve to turn all of thenozzles simultaneously and in the same directions.

The flanges 49 and 51 of the cylinders 45 and 47 are recessed at 129 and131, respectively, to retain the ring gears 125 and 127 in position yetpermit free sliding movement thereof. The ring gears 125 and 127 aremoved in a sequence, as hereafter described, by gears 133 and 135 whichare fixed to shafts 137 and 139. Suitable means, not shown, are providedfor intermittently driving the shafts 137 and 139 and for carrying suchshafts and their driving means with the respective annular members 53and 55 so as to avoid imparting any turning movement to the nozzlesections while such annular members are being moved relative to eachother.

With the various elements of the apparatus in a starting position asshown in FIGS. 4 and 5, a flowable strand-forming material, such as amolten thermoplastic material, is delivered inbetween the cylinders 45and 47, as through a conduit 141. Such flowable strand-forming materialis delivered under pressure and is extruded from the nozzle orifices 113as continuous streams 143 which are set in a liquid 145, which may becool water.

All of the nozzles 97 are simultaneously turned in the same directionand through an angle of 180, or further multiple thereof by the ringgears 125 and 127 which are rotated in opposite directions about theircommon axis by driving the shafts 137 and 139 in opposite directions.The annular members 53 and 55 are held stationary during the turning ofthe nozzles 97 and, once such turning is completed, the nozzles remainstationary while relative movement is effected between the annularmembers 53 and 55.

The purpose of relative movement between the annular members 53 and 55is to rearrange or pair the respective extrusion sections 103 of theindividual nozzles 97 with extrusion sections of other of such nozzlesalternately with the turning of the nozzle sections about theirrespective axes. Thus, such relative movement may be provided byrotating either one of the annular members 53 and 55 about its axis orby rotating both of such annular members in the same direction but atdifferent rates of speed or in opposite directions.

Shifting of the annular member 53 and/or the member 55 is achieved bydriving the gear 79 and/or the gear 81 which are in meshing relationshipwith the teeth 69 and 73 formed in the bottom walls 71 and of therespective annular members. As heretofore mentioned, the ring gears and127 and their driving means are supported so as to shift with therespective annular members 53 and 55 and thereby insure that no torqueis applied to the nozzle sections during this shifting movement.

The degree of relative movement between the annu' lar members must be atleast such as to shift an extrusion section 103 of the individualnozzles 97 into alignment with an extrusion section 103 of a nozzledirectly adjacent thereto. For example, if only one of the annularmembers 53 and 55 is shifted, it would be moved through an angle equalto at least the original angular spacing between the axes of adjacentnozzles, as measured along the surfaces 89 and 91 of such members. Suchone annular member may be moved through a distance equal to a multipleof such angle and such distance may be varied through the method to varythe strand pattern in the resulting net-like structures. Of course, ifthe apparatus includes nozzles having sections of different size and/orsections of different shape, as for example nozzles 97 and 101 shown inFIG. 3, the relative movement between the annular members 53 and 55 mustbe such as to insure that like nozzle extrusion sections are paired witheach other.

Assuming, for purposes of description, that the annular members 53 and55 are both shifted in opposite directions relative to each other, thedistance such members are moved must be at least equal to one-half ofthe angular spacing between the axes of adjacent nozzles, as measuredalong the surfaces 89 and 91 of such surfaces. It will be noted fromFIG. 4 that during this shifting of the annular members 53 and 55, oneof the extrusion sections 103 of each nozzle 97 will move with theannular member 53 while the other of extrusion section 103 and spacersection 109 of each such nozzle will travel with the annular member 55.

After this rearrangement of the nozzle sections, the annular members 53and 55 are again held stationary while the nozzles 97 are again turnedthrough an angle of 180 or further multiple thereof in a direction whichis either the same or opposite to that of their prior tuming movement.Following this turning of the nozzles 97, relative movement between theannular members 53 and S is again effected.

The angle through which the nozzles 97 are turned is important both fromthe standpoint of the net-like structure produced and the practice'ofthe method itself. For example, if the nozzles 97 of the illustratedapparatus are turned through an angle of 360 or further multiple of 180,the strands formed by the streams of strand-forming material extrudedfrom the orifices l 13 will be twisted together at their locations-ofcrossing. In this instance no special care need be taken in thedirection in which the nozzles are turned, providing all are turned inthe same direction. Similarly, each shifting of the annular members 53and 55 may be in the same direction as the prior shifting of suchrespective members.

On the other hand, if the nozzles 97 moved through an angle of only 180during each turning thereof the strands in the resulting net-likestructure will be disposed in a woven or braided relationship. As longas there is no change in the direction of turning of the nozzles 97 nochange is necessary in the direction of shifting of the respectiveannular members 53 and 55. If, however, the nozzles 97 are turned in adirection opposite to their immediately prior turning movement, thenitis essential that the directions in which the annular members 53 and 55are shifted be opposite to that of their immediately prior movement.

As can be seen from the above description, in the manufacture of tubularnet-like structures the method of the present invention can be variedconsiderably, as by shifting the member 53 and/or the member 55, byvarying the angle through which suchmembers are shifted and by changingthe directions in which the nozzles 97 and members 53 and 55 are moved.These variations in the method of the present invention will, of course,provide for different strand patterns in the resulting net-likestructure.

When making net-like structures of a curved configuration which is lessthan 360, the member 53 and/or the member 55 may be shifted and theangle through which such members are moved may be varied to some degree.However, in the manufacture of such curved netlike structures it isessential that only complete nozzles 97 be turned and that theirdirection of turning be reversed after the member 53 and/or the member55 is shifted. Likewise, the direction in which the member 53 and/or 55is shifted must also be reversed after each turning of complete nozzles97.

For example, the support members 53 and 55 may be provided with recesses93 and 95 at spaced intervals along only a 180 arc of their respectiveperipheries 89 and 91. When such recesses 93 and 95 are aligned,circular openings are provided within each of which is disposed .anozzle 97. With flowable strand-forming material being extruded fromeach of the extrusion section orifices, the nozzles 97 are all turned180 in one direction about their respective axes. Either of the members53 and 55 is then shifted for example a distance equal to the angularspacing between nozzles 97 as measured along the peripheries of themembers 53 and 55. Alternatively the members 53 and 55 may be shifted inopposite directions a distance equal to one-half of the angular spacingbetween nozzles.

As a result of this latter movement, an extrusion section 103 of each ofthe outermost nozzles of the series of nozzles 97 are, in effect, movedin opposite directions relative to each other and no longer form part ofcomplete nozzles 97. The complete nozzles 97 are now turned 180 abouttheir respective axes but in a direction opposite to their priorturning. Of course, in such embodiment teeth would be omitted from alongthose portions of the ring gears and 127 which are adjacent to thenozzles sections 103 which are not part of complete nozzles 97 Onceturning of the complete nozzles is effected, either one or both of themembers 53 and 55 are shifted but in a direction opposite to their priormovement.

In making net-like structures of tubular construction or of a curvedconstruction which is less than 360, it will be noted that as a resultof consistently moving the nozzles 97 through an angle of only 180during each turning thereof; that is, alternately with the shifting ofthe support members 53 and 55, the extrusion sections 103 of suchnozzles travel along intersecting sinuous paths and are periodicallyshuttled from one annular member 53 and 55 to the other thereof. Thestreams of flowable strand-forming material issuing from the orifices113 in the nozzle extrusion sections 103 of course follow like paths andwhen set provide a net-like structure having strands which areinterlaced in a woven or braided relationship. As heretofore mentioned,the extruded streams of strand-forming material may be set before orafter they have contacted each other, depending upon thecharacteristics, such as flexibility, strand stability, etc. desired inthe finished structure.

lclaim:

l. A method of making a curved net-like structure by extrusion includingthe steps of extruding a plurality of spaced pairs of continuous streamsof flowable strandforming material, with the streams of each pair ofstreams being located along opposite sides of a common arc, turning thestreams of at least some of the pairs of streams through only an oddnumber of 180 turns, greater than one, about an axis extending betweenthe respective streams of each pair of streams, relatively moving thestreams of each pair of streams in directions concentric with the commonarc to arrange at least certain of the streams of each pair of streamsinto different pairs, setting the streams into strands concomitantlywith their extrusion, and repeating the above sequence of movements.

2. A method as defined in claim 1 wherein the streams of strand-formingmaterial are set prior to any contact therebetween.

3. A method as defined in 'claim 1 wherein the have contacted eachother.

P0403 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent NO,3,686,382 Dated August 22, 1972 Inventor(s) Theodore H. Fairbanks It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Front page, left column, line 6, insert -(73) Assignee: FMC Corporation,Philadelphia,. Pa. Col. 5, line 56, "39" should read 29 Col. 6, line 60,the comma appearing after "nozzle" should be a period Signed and sealedthis 6th day of February 1973.

(SEAL) Attest:

EDWARD MFLETGHER,JR. I ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. A method as defined in claim 1 wherein the streams of strand-formingmaterial are set prior to any contact therebetween.
 3. A method asdefined in claim 1 wherein the streams of strand-forming material areset after they have contacted each other.